At 11:20 AM 20/01/2008 -0500, P.C. Kohler wrote:
>Are we talking about aluminium or alloy? There's a difference.
Aluminum alloy, certainly. Pure aluminum is very soft. I remember seeing a crystal of pure aluminum sagging under its own weight in metallurgy class, until it cold worked itself and gained strength. Forged aluminum parts are also generally stronger than cast. The only use for pure aluminum I know is in the manufacture of aluminum electrolytic capacitors. High strength aluminum alloys used in bicycle construction have become stronger and more reliable and common over the years. However, back in the early 1950s aluminum alloy was still not always chosen over steel for components like stems or even bars. The reason being that aluminum has a finite fatigue life, after which it could fail without warning.
It is interesting that magnesium alloys are not as common in bicycle parts as they have been in aerospace, race cars and motorcycles and even production cars. The VW Beetle had magnesium alloy transmission cases in the late 1950s and today we are finding it used for various car parts to save weight in order to gain fuel economy.
John Betmanis
Woodstock, Ontario
Canada